WO2011096472A1 - Thermally assisted magnetic recording medium and magnetic storage device - Google Patents

Thermally assisted magnetic recording medium and magnetic storage device Download PDF

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WO2011096472A1
WO2011096472A1 PCT/JP2011/052238 JP2011052238W WO2011096472A1 WO 2011096472 A1 WO2011096472 A1 WO 2011096472A1 JP 2011052238 W JP2011052238 W JP 2011052238W WO 2011096472 A1 WO2011096472 A1 WO 2011096472A1
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magnetic
recording medium
magnetic recording
mgo
underlayer
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PCT/JP2011/052238
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French (fr)
Japanese (ja)
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哲也 神邊
篤志 橋本
隆之 福島
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昭和電工株式会社
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Priority to CN201180016253.2A priority Critical patent/CN102822892B/en
Priority to US13/577,085 priority patent/US9818441B2/en
Publication of WO2011096472A1 publication Critical patent/WO2011096472A1/en

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    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/62—Record carriers characterised by the selection of the material
    • G11B5/64—Record carriers characterised by the selection of the material comprising only the magnetic material without bonding agent
    • G11B5/65—Record carriers characterised by the selection of the material comprising only the magnetic material without bonding agent characterised by its composition
    • G11B5/658—Record carriers characterised by the selection of the material comprising only the magnetic material without bonding agent characterised by its composition containing oxygen, e.g. molecular oxygen or magnetic oxide
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/62—Record carriers characterised by the selection of the material
    • G11B5/73—Base layers, i.e. all non-magnetic layers lying under a lowermost magnetic recording layer, e.g. including any non-magnetic layer in between a first magnetic recording layer and either an underlying substrate or a soft magnetic underlayer
    • G11B5/7368—Non-polymeric layer under the lowermost magnetic recording layer
    • G11B5/7369—Two or more non-magnetic underlayers, e.g. seed layers or barrier layers
    • G11B5/737—Physical structure of underlayer, e.g. texture
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B2005/0002—Special dispositions or recording techniques
    • G11B2005/0005—Arrangements, methods or circuits
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B2005/0002—Special dispositions or recording techniques
    • G11B2005/0005—Arrangements, methods or circuits
    • G11B2005/0021—Thermally assisted recording using an auxiliary energy source for heating the recording layer locally to assist the magnetization reversal
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/127—Structure or manufacture of heads, e.g. inductive
    • G11B5/31—Structure or manufacture of heads, e.g. inductive using thin films
    • G11B5/3109—Details
    • G11B5/313—Disposition of layers
    • G11B5/3133—Disposition of layers including layers not usually being a part of the electromagnetic transducer structure and providing additional features, e.g. for improving heat radiation, reduction of power dissipation, adaptations for measurement or indication of gap depth or other properties of the structure
    • G11B5/314—Disposition of layers including layers not usually being a part of the electromagnetic transducer structure and providing additional features, e.g. for improving heat radiation, reduction of power dissipation, adaptations for measurement or indication of gap depth or other properties of the structure where the layers are extra layers normally not provided in the transducing structure, e.g. optical layers

Definitions

  • the present invention relates to a heat-assisted magnetic recording medium and a magnetic storage device using the same.
  • Thermally assisted recording in which writing is performed by irradiating the medium with near-field light or the like to locally heat the surface and reducing the coercive force of the medium, can achieve a surface recording density of about 1 Tbit / inch 2 or more. It is attracting attention as a generation recording system.
  • heat-assisted recording even a recording medium having a coercive force of several tens of kOe at room temperature can be easily written by the recording magnetic field of the current head. For this reason, it becomes possible to use a material having high magnetocrystalline anisotropy Ku of 10 6 J / m 3 for the recording layer, and the magnetic particle size can be reduced to 6 nm or less while maintaining the thermal stability. .
  • the magnetic layer when using the FePt alloy having an L1 0 type crystal structure, the FePt layer must have taken (001) orientation. For this reason, it is desirable to use (100) -oriented MgO for the underlayer. (100) plane of MgO, L1 0 type (001) of the FePt for both good lattice matching with, by forming an L1 0 type FePt magnetic layer on the MgO underlayer oriented (100), the magnetic layer Can have (001) orientation.
  • Non-Patent Document 1 describes that the magnetic particle diameter can be reduced to 5 nm by adding 20 vol% TiO 2 to FePt.
  • Non-Patent Document 2 describes that the magnetic particle diameter can be reduced to 2.9 nm by adding 50% by volume of SiO 2 to FePt.
  • the magnetic layer of the heat-assisted recording medium to use L1 0 FePt alloy structure or the like having a high Ku is preferable.
  • L1 0 FePt alloy structure or the like having a high Ku
  • a grain boundary segregation material such as SiO 2 or C
  • an object of the present invention is to provide a heat-assisted recording medium having fine magnetic crystal grains, low particle size dispersion, sufficiently weak exchange coupling between magnetic particles, and low coercive force dispersion. There is to do.
  • Another object of the present invention is to provide a magnetic storage device having a heat-assisted recording medium having the above characteristics and excellent in electromagnetic conversion characteristics such as SN ratio and writeability.
  • the following heat-assisted magnetic recording medium and magnetic storage device are provided.
  • a substrate a plurality of base layer formed on the substrate, a magnetic recording medium having a magnetic layer mainly composed of an alloy having an L1 0 structure, at least one underlayer is a MgO main And at least one kind selected from SiO 2 , TiO 2 , Cr 2 O 3 , Al 2 O 3 , Ta 2 O 5 , ZrO 2 , Y 2 O 3 , CeO 2 , MnO, TiO and ZnO
  • a heat-assisted magnetic recording medium comprising an oxide.
  • the magnetic layer is mainly composed of FePt or CoPt alloy having an L1 0 structure and, SiO 2, TiO 2, Cr 2 O 3, Al 2 O 3, Ta 2 O 5, ZrO 2, Y 2 O 3
  • the magnetic recording medium Is a heat-assisted medium according to any one of the above (1) to (8).
  • the heat-assisted recording medium of the present invention has the characteristics that the magnetic crystal grains are fine, the particle size dispersion is low, the exchange coupling between the magnetic particles is sufficiently weak, and the coercive force dispersion is low. Therefore, a magnetic storage device using this heat-assisted recording medium is excellent in electromagnetic conversion characteristics, in particular, SN ratio and writeability.
  • the figure showing an example of the laminated constitution of the magnetic recording medium of this invention The figure showing another example of the laminated constitution of the magnetic recording medium of this invention 1 is a perspective view illustrating an example of a magnetic storage device according to the present invention.
  • the figure showing an example of the magnetic head concerning this invention is a perspective view illustrating an example of a magnetic storage device according to the present invention.
  • Thermally assisted magnetic recording medium of the present invention includes a substrate and a plurality of base layer formed on the substrate, a magnetic recording medium comprising a magnetic layer mainly composed of an alloy having an L1 0 structure, the underlying layer At least one of which is mainly composed of MgO and is composed of SiO 2 , TiO 2 , Cr 2 O 3 , Al 2 O 3 , Ta 2 O 5 , ZrO 2 , Y 2 O 3 , CeO 2 , MnO, TiO and ZnO. It contains at least one selected oxide.
  • the particle diameter of the MgO underlayer is approximately 10 nm or less. However, in order to realize a surface recording density of 1 Tbit / inch 2 or more, it is necessary to reduce the magnetic particle size to approximately 6 nm or less. Therefore, the particle diameter of the MgO underlayer is more preferably 6 nm or less.
  • the amount of oxide added to MgO is not particularly limited as long as it is within a range that does not significantly deteriorate the NaCl structure of the MgO underlayer and the (100) orientation, but the total amount of addition is based on the entire underlayer. It is desirable to be within the range of 2 mol% to 40 mol%. If it is less than 2 mol%, the refinement of MgO becomes insufficient, and if it exceeds 40 mol%, the NaCl structure deteriorates, which is not desirable.
  • the magnetic layer, FePt alloy or CoPt alloy having an L1 0 structure is preferably used.
  • a grain boundary segregation material in the alloy SiO 2 , TiO 2 , Cr 2 O 3 , Al 2 O 3 , Ta 2 O 5 , ZrO 2 , Y 2 O 3 , CeO 2 , MnO, TiO, ZnO, etc. Oxides, C, and mixtures thereof may be added.
  • the magnetic layer, FePt alloy or CoPt alloy having an L1 0 structure take the shed granular structure by the grain boundary polarization ⁇ fee.
  • the content of the grain boundary segregation material is preferably 30% by volume or more based on the entire magnetic layer, but more preferably 40% by volume or more in order to further increase the separation width between the magnetic particles.
  • the upper limit of the content of the grain boundary polarization ⁇ fee preferable to be 60% by volume.
  • the mol fraction of each oxide needs to be converted so that the volume fraction falls within the above range.
  • the addition amount be approximately 10 mol% to 30 mol% based on the entire magnetic layer.
  • approximately 10 to 40 mol% is desirable based on the entire magnetic layer.
  • the amount of C used for the grain boundary segregation material is preferably in the range of 10 at% or more and 70 at% or less based on the entire magnetic layer.
  • the crystal grain size of the FePt alloy or CoPt alloy can be reduced to 6 nm or less, and at the same time, the grain boundary width should be 1 nm or more to sufficiently reduce exchange coupling between magnetic particles. Can do.
  • underlying layer mainly composed of MgO is preferably taking the (100) orientation.
  • a Ta base layer may be formed on a glass substrate and MgO as a main component may be formed on the Ta base layer.
  • the Cr layer or the Cr alloy layer exhibits (100) orientation. Therefore, by forming an MgO layer on this, the (100) orientation can be taken in the MgO layer.
  • the Cr alloy include CrTi, CrMo, CrV, CrW, CrMo, CrRu, and CrMn.
  • the thermally-assisted magnetic recording medium of the present invention it is essential that at least one of the plurality of underlayers formed on the substrate is an underlayer containing the above MgO as a main component and containing a specific oxide.
  • the other underlayers are not particularly limited, and those similar to general magnetic recording media can be used.
  • the foundation layer other than the foundation layer mainly composed of MgO include the orientation control layer composed of the above-mentioned Ta; and the orientation control composed of the above-described Cr or an alloy having a BCC structure mainly composed of Cr.
  • a heat sink layer made of an alloy material having a high thermal conductivity containing these as a main component; a soft magnetic underlayer made of Co or the main component of Co for improving write characteristics Can be mentioned. Furthermore, an adhesion layer for improving adhesion with the substrate can be formed.
  • FIG. 1 shows an example of the layer structure of the magnetic recording medium produced in this example.
  • a Ni-50 atom (at)% Ti alloy underlayer (102) having a thickness of 30 nm and a Co-20 at% Ta-5 at% B alloy having a thickness of 25 nm are formed on a heat-resistant glass substrate (101). After forming (103) and heating to 250 ° C., a 10 nm thick Cr layer (104) was formed.
  • an underlayer (105) containing MgO as a main component is formed to 5 nm, the substrate is heated to 420 ° C., and then a 6 nm thick (Fe-55 at% Pt) -18 mol% TiO 2 magnetic layer (106), 3 nm thick A carbon protective film (107) was formed.
  • Table 1 shows values of the coercive force Hc and the coercive force dispersion ⁇ Hc / Hc of the medium of this example and the comparative example.
  • ⁇ Hc / Hc is the value of IEEE Trans. Magn. , Vol. 27, pp 4975-4977, 1991, and measured at room temperature.
  • the magnetic field when the magnetization value is 50% of the saturation value is measured, and ⁇ Hc / Hc is calculated from the difference between the two assuming that the Hc distribution is a Gaussian distribution. Calculated.
  • the ⁇ Hc / Hc of the example medium was a low value of 0.3 or less, whereas the ⁇ Hc / Hc of the comparative example medium was 0.52, which was significantly higher than that of the example medium. .
  • dispersion of coercive force can be reduced by adding an oxide such as SiO 2 to the MgO underlayer.
  • the magnetic layer includes FePt—SiO 2 , FePt—Cr 2 O 3 , FePt—Al 2 O 3 , FePt—Ta 2 O 5 , FePt—ZrO 2 , FePt—Y.
  • FePt—CeO 2 , FePt—MnO, FePt—TiO, and FePt—ZnO when used, the dispersion of coercive force can be reduced by forming an underlayer composed of MgO and an oxide door. all right. It is also possible to use a magnetic layer made of CoPt alloy and the oxide, or C having an L1 0 structure.
  • FIG. 2 shows another example of the layer structure of the magnetic recording medium manufactured in this example.
  • a soft magnetic substrate comprising a Ni-50 at% Ta alloy seed layer (202) with a thickness of 10 nm and a Co-28 at% Fe-5 at% Zr-3 at% Ta alloy with a thickness of 50 nm on a heat resistant glass substrate (201).
  • a base layer (203) and a 7 nm thick Ta underlayer (204) were formed.
  • an underlayer (205) containing MgO as a main component is formed to 3 nm, the substrate is heated to 450 ° C., and then a 10 nm thick (Fe-50 at% Pt-10 at% Cu) -40 at% C magnetic layer (206) A carbon protective film (207) having a thickness of 3 nm was formed.
  • the underlayer mainly composed of MgO includes MgO-18 mol% SiO 2 , MgO-5 mol% SiO 2 -5 mol% Cr 2 O 3 , MgO-5 mol% TiO 2 —Cr 2 O 3 , MgO-4 mol% TiO 2. -3at% ZrO 2, MgO-8mol % Cr 2 O 3, MgO-10mol% Al 2 O 3 -3at% Ta 2 O 5, MgO-5mol% Y 2 O 3, were used MgO-10at% TiO-2molZnO . Further, as a comparative example, a medium using an MgO underlayer to which no oxide was added was produced. Furthermore, in order to perform planar TEM observation of the base layer containing MgO as a main component, a sample was prepared in which no magnetic layer was formed on the base layer containing MgO as a main component.
  • Table 2 shows the average particle size ⁇ D> of the magnetic layer of the medium of this example and the value of particle size dispersion ⁇ / ⁇ D> normalized by the average particle size.
  • the average particle diameter of the media of this example was in the range of 5.5 to 6.4 nm.
  • the particle size dispersion ⁇ / ⁇ D> normalized by the average particle size showed a low value of 0.22 or less.
  • the average particle size of the magnetic layer of the comparative example medium was almost the same as that of the medium of this example, but the particle size dispersion ⁇ / ⁇ D> normalized by the average particle size is 0.32. It was significantly higher than the example medium.
  • the magnetic storage device includes a magnetic recording medium (701), a driving unit (702) for rotating the magnetic recording medium (701), a magnetic head (703), and a driving unit (70) for moving the head. And a recording / reproducing signal processing system (705).
  • Fig. 4 shows the configuration of the magnetic head.
  • the recording head (801) includes an upper magnetic pole (802), a lower magnetic pole (803), and a PSIM (Planar Solid Immersion Mirror) (804) sandwiched therebetween.
  • PSIM is, for example, Jpn. , J. Appl. Phys. , Vol45, No. 2B, pp1314-1320 (2006) can be used. That is, a near-field light generating part (805) is formed at the tip of the PSIM (804).
  • the semiconductor light source (808) having a wavelength of 650 nm, for example, is irradiated from the laser light source (807) to the PSIM grating unit (806), and the near-field light is condensed on the near-field light generation unit at the PSIM tip.
  • the medium (810) can be heated by the near-field light (809) generated from the generation unit.
  • the reproducing head (811) includes an upper shield (812) and a lower shield (813), and a TMR element (814) sandwiched between them.
  • the medium of this example was heated with the above-mentioned head, a signal with a linear recording density of 1600 kFCI (kilo flux changes per inch) was recorded, and the electromagnetic conversion characteristics were measured. Table 3 shows the measurement results.
  • OW overwrite characteristic
  • All of the media of this example exhibited a high medium SN ratio (SNR) of 15.3 dB or more and good overwrite characteristics of 30.1 dB or more.
  • SNR medium SN ratio
  • the SNR and the overwriting characteristics of the comparative example medium using the MgO underlayer to which no oxide was added were significantly lower than those of the example medium.
  • the heat-assisted recording medium of the present invention has the characteristics that the magnetic crystal grains are fine, the particle size dispersion is low, the exchange coupling between the magnetic particles is sufficiently weak, and the coercive force dispersion is low. Therefore, a magnetic storage device using this heat-assisted recording medium is expected to be widely used as a magnetic recording method capable of high-density recording because of excellent electromagnetic conversion characteristics, in particular, SN ratio and writability. .

Abstract

Disclosed is a thermally assisted magnetic recording medium comprising a substrate, a plurality of undercoat layers formed on the substrate, and a magnetic layer which comprises, as the main component, an alloy having an L10 structure, wherein at least one of the undercoat layers comprises MgO as a main component and contains at least one oxide selected from among SiO2, TiO2, Cr2O3, Al2O3, Ta2O5, ZrO2, Y2O3, CeO2, MnO, TiO, and ZnO. The thermally assisted recording medium has such properties that the magnetic grains have an exceedingly small diameter, the exchange coupling among the magnetic grains is sufficiently weak, and the dispersion of coercive force is low.

Description

熱アシスト磁気記録媒体及び磁気記憶装置Thermally assisted magnetic recording medium and magnetic storage device
　本発明は熱アシスト磁気記録媒体、及びそれを用いた磁気記憶装置に関する。 The present invention relates to a heat-assisted magnetic recording medium and a magnetic storage device using the same.
　媒体に近接場光等を照射して表面を局所的に加熱し、媒体の保磁力を低下させて書き込みを行う熱アシスト記録は、約１Ｔｂｉｔ／ｉｎｃｈ２またはそれ以上の面記録密度を実現できる次世代記録方式として注目されている。熱アシスト記録を用いた場合、室温における保磁力が数十ｋＯｅの記録媒体でも、現状ヘッドの記録磁界により容易に書き込みを行うことができる。このため、記録層に１０６Ｊ／ｍ３台の高い結晶磁気異方性Ｋｕを有する材料を使用することが可能となり、熱安定性を維持したまま、磁性粒径を６ｎｍ以下まで微細化できる。このような高Ｋｕ材料としては、Ｌ１０型結晶構造を有するＦｅＰｔ合金（Ｋｕ～７×１０６Ｊ／ｍ３）や、ＣｏＰｔ合金（Ｋｕ～５×１０６Ｊ／ｍ３）等が知られている。 Thermally assisted recording, in which writing is performed by irradiating the medium with near-field light or the like to locally heat the surface and reducing the coercive force of the medium, can achieve a surface recording density of about 1 Tbit / inch 2 or more. It is attracting attention as a generation recording system. When heat-assisted recording is used, even a recording medium having a coercive force of several tens of kOe at room temperature can be easily written by the recording magnetic field of the current head. For this reason, it becomes possible to use a material having high magnetocrystalline anisotropy Ku of 10 6 J / m 3 for the recording layer, and the magnetic particle size can be reduced to 6 nm or less while maintaining the thermal stability. . Examples of such high Ku material, FePt alloy having an L1 0 type crystal structure (Ku ~ 7 × 10 6 J / m 3) and, CoPt alloy (Ku ~ 5 × 10 6 J / m 3) or the like is known ing.
　磁性層に、Ｌ１０型結晶構造を有するＦｅＰｔ合金を用いる場合、該ＦｅＰｔ層は（００１）配向をとっている必要がある。このため、下地層には（１００）配向したＭｇＯを用いるのが望ましい。ＭｇＯの（１００）面は、Ｌ１０型ＦｅＰｔの（００１）面と格子整合性が良いため、（１００）配向したＭｇＯ下地層上にＬ１０型ＦｅＰｔ磁性層を形成することにより、該磁性層に（００１）配向をとらせることができる。 The magnetic layer, when using the FePt alloy having an L1 0 type crystal structure, the FePt layer must have taken (001) orientation. For this reason, it is desirable to use (100) -oriented MgO for the underlayer. (100) plane of MgO, L1 0 type (001) of the FePt for both good lattice matching with, by forming an L1 0 type FePt magnetic layer on the MgO underlayer oriented (100), the magnetic layer Can have (001) orientation.
　一方、熱アシスト記録媒体においても、媒体ノイズを低減し、ＳＮ比を向上させるためには、磁性粒径の微細化が必須である。磁性粒径を微細化するには、磁性層にＳｉＯ２等の酸化物からなる粒界偏析材料を添加することが効果的である。これは、磁性層が、ＦｅＰｔ結晶がＳｉＯ２で囲まれたグラニュラー構造となるためである。磁性結晶の粒径は、粒界偏析材料の添加量を増やすことによって微細化できる。非特許文献１には、ＦｅＰｔに２０体積％のＴｉＯ２を添加することにより、磁性粒径を５ｎｍまで低減できることが記載されている。また、非特許文献２には、ＦｅＰｔに５０体積％のＳｉＯ２を添加することにより、磁性粒径を２．９ｎｍまで低減できることが記載されている。 On the other hand, also in the heat-assisted recording medium, in order to reduce the medium noise and improve the SN ratio, it is essential to reduce the magnetic particle diameter. In order to reduce the magnetic particle size, it is effective to add a grain boundary segregation material made of an oxide such as SiO 2 to the magnetic layer. This is because the magnetic layer has a granular structure in which the FePt crystal is surrounded by SiO 2 . The grain size of the magnetic crystal can be refined by increasing the amount of grain boundary segregation material added. Non-Patent Document 1 describes that the magnetic particle diameter can be reduced to 5 nm by adding 20 vol% TiO 2 to FePt. Non-Patent Document 2 describes that the magnetic particle diameter can be reduced to 2.9 nm by adding 50% by volume of SiO 2 to FePt.
　熱アシスト記録媒体の磁性層には、高いＫｕを有するＬ１０構造のＦｅＰｔ合金等を用いるのが望ましい。また、高い媒体ＳＮ比を実現するには、磁性結晶粒を微細化すると同時に、磁性粒子間の交換結合を十分に低減する必要がある。これを実現するには、磁性層にＳｉＯ２やＣ等の粒界偏析材料を添加することが有効である。磁性粒径を概ね６ｎｍ以下まで微細化し、かつ、交換結合を十分に低減するには、３０－４０体積％以上の粒界偏析材料を添加する必要がある。 The magnetic layer of the heat-assisted recording medium, to use L1 0 FePt alloy structure or the like having a high Ku is preferable. In order to realize a high medium S / N ratio, it is necessary to sufficiently reduce the exchange coupling between the magnetic grains while simultaneously miniaturizing the magnetic crystal grains. In order to realize this, it is effective to add a grain boundary segregation material such as SiO 2 or C to the magnetic layer. In order to reduce the magnetic particle size to approximately 6 nm or less and sufficiently reduce exchange coupling, it is necessary to add 30-40% by volume or more of grain boundary segregation material.
　しかし、粒界偏析材料を多量に添加すると、Ｌ１０構造を有するＦｅＰｔ結晶の規則度が劣化し、Ｋｕが低下する。このため、Ｌ１０－ＦｅＰｔ結晶粒の高い規則度を維持したまま、磁性結晶粒を微細化し、粒子間の交換結合を低減する必要がある。
　また、粒界偏析材料を多量に添加すると、保磁力分散が著しく増大する。これは、粒径分散や、粒界幅分散が増大するためと考えられる。よって、保磁力分散の低減も、高い媒体ＳＮ比を実現する上での重要な課題である。 However, the addition a large amount of grain boundary polarization析材fee is deteriorated degree of order of FePt crystals having an L1 0 structure, Ku is lowered. For this reason, it is necessary to refine the magnetic crystal grains and reduce the exchange coupling between the grains while maintaining the high degree of order of the L1 0 -FePt crystal grains.
Further, when a large amount of grain boundary segregation material is added, the coercive force dispersion is remarkably increased. This is thought to be due to an increase in particle size dispersion and grain boundary width dispersion. Therefore, reduction of coercive force dispersion is also an important issue in realizing a high medium SN ratio.
　上記の背景技術に鑑みて、本発明の目的は、磁性結晶粒が微細で粒径分散が低く、磁性粒子間の交換結合が十分に弱く、かつ、保磁力分散が低い熱アシスト記録媒体を提供することにある。
　本発明の他の目的は、上記の特性を有する熱アシスト記録媒体を具え、ＳＮ比と書き込み性などの電磁変換特性に優れた磁気記憶装置を提供することにある。 In view of the above background art, an object of the present invention is to provide a heat-assisted recording medium having fine magnetic crystal grains, low particle size dispersion, sufficiently weak exchange coupling between magnetic particles, and low coercive force dispersion. There is to do.
Another object of the present invention is to provide a magnetic storage device having a heat-assisted recording medium having the above characteristics and excellent in electromagnetic conversion characteristics such as SN ratio and writeability.
　かくして、本発明によれば、以下の熱アシスト磁気記録媒体、および磁気記憶装置が提供される。 Thus, according to the present invention, the following heat-assisted magnetic recording medium and magnetic storage device are provided.
（１）基板と、該基板上に形成された複数の下地層と、Ｌ１０構造を有する合金を主成分とする磁性層を有する磁気記録媒体において、該下地層の少なくとも一つが、ＭｇＯを主成分とし、かつ、ＳｉＯ２、ＴｉＯ２、Ｃｒ２Ｏ３、Ａｌ２Ｏ３、Ｔａ２Ｏ５、ＺｒＯ２、Ｙ２Ｏ３、ＣｅＯ２、ＭｎＯ、ＴｉＯおよびＺｎＯから選択される少なくとも一種類の酸化物を含有していることを特徴とする熱アシスト磁気記録媒体。 (1) a substrate, a plurality of base layer formed on the substrate, a magnetic recording medium having a magnetic layer mainly composed of an alloy having an L1 0 structure, at least one underlayer is a MgO main And at least one kind selected from SiO 2 , TiO 2 , Cr 2 O 3 , Al 2 O 3 , Ta 2 O 5 , ZrO 2 , Y 2 O 3 , CeO 2 , MnO, TiO and ZnO A heat-assisted magnetic recording medium comprising an oxide.
（２）ＭｇＯを主成分とする下地層に含まれる酸化物の量が、下地層全体に基づき、２ｍｏｌ％～４０ｍｏｌ％の範囲内である上記（１）に記載の熱アシスト磁気記録媒体。
（３）ＭｇＯを主成分とする下地層が、Ｃｒからなる層、またはＣｒを主成分とするＢＣＣ構造を有するＣｒ合金からなる下地層上に形成されている上記（１）または（２）に記載の熱アシスト磁気記録媒体。
（４）ＭｇＯを主成分とする下地層が、Ｔａ下地層上に形成されている上記（１）または（２）に記載の熱アシスト磁気記録媒体。
（５）ＭｇＯを主成分とする下地層の平均粒径が１０ｎｍ以下である上記（１）～（４）の何れかに記載の熱アシスト磁気記録媒体。 (2) The heat-assisted magnetic recording medium according to (1), wherein the amount of oxide contained in the underlayer containing MgO as a main component is in the range of 2 mol% to 40 mol% based on the entire underlayer.
(3) In the above (1) or (2), the base layer mainly composed of MgO is formed on a layer composed of Cr or a base layer composed of Cr alloy having a BCC structure mainly composed of Cr. The heat-assisted magnetic recording medium described.
(4) The heat-assisted magnetic recording medium according to (1) or (2), wherein the underlayer mainly composed of MgO is formed on the Ta underlayer.
(5) The heat-assisted magnetic recording medium as described in any one of (1) to (4) above, wherein the average particle size of the underlayer mainly composed of MgO is 10 nm or less.
（６）磁性層がＬ１０構造を有するＦｅＰｔまたはＣｏＰｔ合金を主成分とし、かつ、ＳｉＯ２、ＴｉＯ２、Ｃｒ２Ｏ３、Ａｌ２Ｏ３、Ｔａ２Ｏ５、ＺｒＯ２、Ｙ２Ｏ３、ＣｅＯ２、ＭｎＯ、ＴｉＯ、ＺｎＯ、およびＣから選択される少なくとも一種類の酸化物または元素を含有している上記（１）～（４）のいずれかに記載の熱アシスト磁気記録媒体。
（７）磁性層に含まれる酸化物の量が、磁性層全体に基づき、１０ｍｏｌ％以上、４０ｍｏｌ％以下の範囲内である上記（６）に記載の熱アシスト磁気記録媒体。 (6) the magnetic layer is mainly composed of FePt or CoPt alloy having an L1 0 structure and, SiO 2, TiO 2, Cr 2 O 3, Al 2 O 3, Ta 2 O 5, ZrO 2, Y 2 O 3 The heat-assisted magnetic recording medium according to any one of the above (1) to (4), which contains at least one kind of oxide or element selected from C, CeO 2 , MnO, TiO, ZnO, and C.
(7) The heat-assisted magnetic recording medium according to (6), wherein the amount of oxide contained in the magnetic layer is in the range of 10 mol% or more and 40 mol% or less based on the entire magnetic layer.
（８）磁性層に含まれるＣの量が、磁性層全体に基づき、１０ａｔ％以上、７０ａｔ％以下の範囲内である上記（６）に記載の熱アシスト磁気記録媒体。
（９）磁気記録媒体と、該磁気記録媒体を回転させるための駆動部と、該磁気記録媒体を加熱するためのレーザー発生部と、該レーザー発生部から発生したレーザー光をヘッド先端まで導く導波路と、ヘッド先端に取り付けられた近接場光発生部を備えた磁気ヘッドと、該磁気ヘッドを移動させるための駆動部と、記録再生信号処理系から構成さる磁気記憶装置において、該磁気記録媒体が上記（１）～（８）のいずれかに記載の熱アシスト媒体であることを特徴とする磁気記憶装置。 (8) The heat-assisted magnetic recording medium according to (6), wherein the amount of C contained in the magnetic layer is in the range of 10 at% or more and 70 at% or less based on the entire magnetic layer.
(9) A magnetic recording medium, a driving unit for rotating the magnetic recording medium, a laser generating unit for heating the magnetic recording medium, and a laser beam generated from the laser generating unit for guiding the laser light to the head tip. In a magnetic storage device comprising a waveguide, a magnetic head having a near-field light generating unit attached to the tip of the head, a driving unit for moving the magnetic head, and a recording / reproducing signal processing system, the magnetic recording medium Is a heat-assisted medium according to any one of the above (1) to (8).
　本発明の熱アシスト記録媒体は、磁性結晶粒が微細で粒径分散が低く、磁性粒子間の交換結合が十分に弱く、かつ、保磁力分散が低いという特長を有する。したがって、この熱アシスト記録媒体を用いた磁気記憶装置は、電磁変換特性、特に、ＳＮ比と書き込み性に優れている。 The heat-assisted recording medium of the present invention has the characteristics that the magnetic crystal grains are fine, the particle size dispersion is low, the exchange coupling between the magnetic particles is sufficiently weak, and the coercive force dispersion is low. Therefore, a magnetic storage device using this heat-assisted recording medium is excellent in electromagnetic conversion characteristics, in particular, SN ratio and writeability.
本発明の磁気記録媒体の層構成の一例を表す図The figure showing an example of the laminated constitution of the magnetic recording medium of this invention 本発明の磁気記録媒体の層構成の他の一例を表す図The figure showing another example of the laminated constitution of the magnetic recording medium of this invention 本発明に係わる磁気記憶装置の一例を表す傾視図1 is a perspective view illustrating an example of a magnetic storage device according to the present invention. 本発明に係わる磁気ヘッドの一例を表す図The figure showing an example of the magnetic head concerning this invention
　以下、本発明を適用した熱アシスト磁気記録媒体及び磁気記憶装置について、図面を参照して詳細に説明する。なお、以下の説明で用いる図面は、特徴をわかりやすくするために、便宜上特徴となる部分を拡大して示している場合があり、各構成要素の寸法比率などが実際と同じであるとは限らない。 Hereinafter, a thermally assisted magnetic recording medium and a magnetic storage device to which the present invention is applied will be described in detail with reference to the drawings. In addition, in the drawings used in the following description, in order to make the features easy to understand, there are cases where the portions that become the features are enlarged for the sake of convenience, and the dimensional ratios of the respective components are not always the same as the actual ones. Absent.
　本願発明の熱アシスト磁気記録媒体は、基板と、該基板上に形成された複数の下地層と、Ｌ１０構造を有する合金を主成分とする磁性層からなる磁気記録媒体において、該下地層の少なくとも一つが、ＭｇＯを主成分とし、かつ、ＳｉＯ２、ＴｉＯ２、Ｃｒ２Ｏ３、Ａｌ２Ｏ３、Ｔａ２Ｏ５、ＺｒＯ２、Ｙ２Ｏ３、ＣｅＯ２、ＭｎＯ、ＴｉＯおよびＺｎＯから選択される少なくとも一種類の酸化物を含有していることを特徴とする。 Thermally assisted magnetic recording medium of the present invention includes a substrate and a plurality of base layer formed on the substrate, a magnetic recording medium comprising a magnetic layer mainly composed of an alloy having an L1 0 structure, the underlying layer At least one of which is mainly composed of MgO and is composed of SiO 2 , TiO 2 , Cr 2 O 3 , Al 2 O 3 , Ta 2 O 5 , ZrO 2 , Y 2 O 3 , CeO 2 , MnO, TiO and ZnO. It contains at least one selected oxide.
　複数の磁性結晶粒が一つの大きなＭｇＯ下地層上に形成されていると、磁性粒子間の交換結合を十分に低減することができない。しかしながら、ＭｇＯ下地層の粒径を微細化することによって、一つのＭｇＯ結晶粒の上に一つの磁性結晶粒が成長する“Ｏｎｅ－ｂｙ－ｏｎｅ成長”が促進される。これにより、磁性粒子間の分離が促進され、交換結合を低減できる。また、磁性粒径も均一化されるため、保磁力分散も低減できる。ＭｇＯ下地層の粒径は、ＳｉＯ２、ＴｉＯ２、Ｃｒ２Ｏ３、Ａｌ２Ｏ３、Ｔａ２Ｏ５、ＺｒＯ２、Ｙ２Ｏ３、ＣｅＯ２、ＭｎＯ、ＴｉＯ、ＺｎＯの酸化物を添加することによって微細化できる。 If a plurality of magnetic crystal grains are formed on one large MgO underlayer, exchange coupling between the magnetic grains cannot be sufficiently reduced. However, by reducing the grain size of the MgO underlayer, “One-by-one growth” in which one magnetic crystal grain grows on one MgO crystal grain is promoted. Thereby, separation between magnetic particles is promoted, and exchange coupling can be reduced. Further, since the magnetic particle diameter is also made uniform, the coercive force dispersion can be reduced. The particle size of the MgO underlayer, SiO 2, TiO 2, Cr 2 O 3, Al 2 O 3, Ta 2 O 5, ZrO 2, Y 2 O 3, CeO 2, MnO, TiO, oxides of ZnO added Can be made finer.
　磁性結晶粒の分離を十分に促進するには、ＭｇＯ下地層の粒径を概ね１０ｎｍ以下とするのが好ましい。但し、１Ｔｂｉｔ／ｉｎｃｈ２以上の面記録密度を実現するには、磁性粒径を概ね６ｎｍ以下に微細化する必要がある。よって、ＭｇＯ下地層の粒径も６ｎｍ以下とすることがより好ましい。
　ＭｇＯへ添加する酸化物の添加量は、ＭｇＯ下地層のＮａＣｌ構造と、（１００）配向を大幅に劣化させない範囲内であれば特に制限はないが、添加量の合計は、下地層全体に基づき、２ｍｏｌ％～４０ｍｏｌ％の範囲内とするのが望ましい。２ｍｏｌ％を下回ると、ＭｇＯの微細化が不十分となり、４０ｍｏｌ％を上回ると、ＮａＣｌ構造が劣化するため、望ましくない。 In order to sufficiently promote the separation of the magnetic crystal grains, it is preferable that the particle diameter of the MgO underlayer is approximately 10 nm or less. However, in order to realize a surface recording density of 1 Tbit / inch 2 or more, it is necessary to reduce the magnetic particle size to approximately 6 nm or less. Therefore, the particle diameter of the MgO underlayer is more preferably 6 nm or less.
The amount of oxide added to MgO is not particularly limited as long as it is within a range that does not significantly deteriorate the NaCl structure of the MgO underlayer and the (100) orientation, but the total amount of addition is based on the entire underlayer. It is desirable to be within the range of 2 mol% to 40 mol%. If it is less than 2 mol%, the refinement of MgO becomes insufficient, and if it exceeds 40 mol%, the NaCl structure deteriorates, which is not desirable.
　磁性層には、Ｌ１０構造を有するＦｅＰｔ合金またはＣｏＰｔ合金が好ましく用いられる。また、前記合金に粒界偏析材料として、ＳｉＯ２、ＴｉＯ２、Ｃｒ２Ｏ３、Ａｌ２Ｏ３、Ｔａ２Ｏ５、ＺｒＯ２、Ｙ２Ｏ３、ＣｅＯ２、ＭｎＯ、ＴｉＯ、ＺｎＯ等の酸化物や、Ｃ、および、これらの混合物を添加してもよい。この場合、磁性層は、Ｌ１０構造を有するＦｅＰｔ合金またはＣｏＰｔ合金が、前記粒界偏析材料によって分断されたグラニュラー構造をとる。 The magnetic layer, FePt alloy or CoPt alloy having an L1 0 structure is preferably used. Moreover, as a grain boundary segregation material in the alloy, SiO 2 , TiO 2 , Cr 2 O 3 , Al 2 O 3 , Ta 2 O 5 , ZrO 2 , Y 2 O 3 , CeO 2 , MnO, TiO, ZnO, etc. Oxides, C, and mixtures thereof may be added. In this case, the magnetic layer, FePt alloy or CoPt alloy having an L1 0 structure, take the shed granular structure by the grain boundary polarization析材fee.
　粒界偏析材料の含有率は、磁性層全体に基づき、３０体積％以上であることが好ましいが、磁性粒子間の分離幅をより広げるには、４０体積％以上であることがより好ましい。但し、粒界偏析材料を過度に添加すると、Ｌ１０構造が劣化するため、粒界偏析材料の含有率の上限を６０体積％とするのが好ましい。 The content of the grain boundary segregation material is preferably 30% by volume or more based on the entire magnetic layer, but more preferably 40% by volume or more in order to further increase the separation width between the magnetic particles. However, excessive addition of grain boundary polarization析材fees, L1 0 since the structure is degraded, the upper limit of the content of the grain boundary polarization析材fee preferable to be 60% by volume.
　粒界偏析材料に用いる酸化物の１ｍｏｌ％当りの体積は、酸化物の種類によって異なるため、各酸化物のｍｏｌ分率は、体積分率が上記範囲内となるように換算する必要がある。例えば、粒界偏析材料にＳｉＯ２を用いた場合、添加量は、磁性層全体に基づき、概ね１０ｍｏｌ％から３０ｍｏｌ％とするのが望ましい。他の酸化物に関しても、磁性層全体に基づき、概ね１０ｍｏｌ％から４０ｍｏｌ％程度が望ましい。
　粒界偏析材料に用いるＣの量は、磁性層全体に基づき、１０ａｔ％以上、７０ａｔ％以下の範囲内であることが好ましい。 Since the volume per 1 mol% of the oxide used for the grain boundary segregation material varies depending on the type of oxide, the mol fraction of each oxide needs to be converted so that the volume fraction falls within the above range. For example, when SiO 2 is used as the grain boundary segregation material, it is desirable that the addition amount be approximately 10 mol% to 30 mol% based on the entire magnetic layer. Regarding other oxides as well, approximately 10 to 40 mol% is desirable based on the entire magnetic layer.
The amount of C used for the grain boundary segregation material is preferably in the range of 10 at% or more and 70 at% or less based on the entire magnetic layer.
　上記粒界偏析材料を添加することにより、ＦｅＰｔ合金またはＣｏＰｔ合金の結晶粒径を６ｎｍ以下に微細化できると同時に、粒界幅を１ｎｍ以上とし、磁性粒子間の交換結合を十分に低減することができる。 By adding the grain boundary segregation material, the crystal grain size of the FePt alloy or CoPt alloy can be reduced to 6 nm or less, and at the same time, the grain boundary width should be 1 nm or more to sufficiently reduce exchange coupling between magnetic particles. Can do.
　Ｌ１０構造を有するＦｅＰｔまたはＣｏＰｔ合金に（００１）配向をとらせるため、ＭｇＯを主成分とする下地層は、（１００）配向をとっていることが好ましい。ＭｇＯを主成分とする下地層に（１００）配向をとらせるには、例えば、ガラス基板上にＴａ下地層を形成し、該Ｔａ下地層の上にＭｇＯを主成分とするを形成すればよい。また、加熱したガラス基板上にＣｒ層、またはＣｒを主成分とするＢＣＣ構造の合金層を形成した場合、該Ｃｒ層、またはＣｒ合金層は（１００）配向を示す。よって、この上にＭｇＯ層を形成することによっても、該ＭｇＯ層に（１００）配向をとらせることができる。上記Ｃｒ合金としては、具体的にＣｒＴｉ、ＣｒＭｏ、ＣｒＶ、ＣｒＷ、ＣｒＭｏ、ＣｒＲｕ、ＣｒＭｎ等を用いることができる。 Because it assumes a (001) oriented FePt or CoPt alloy having an L1 0 structure, underlying layer mainly composed of MgO is preferably taking the (100) orientation. In order to obtain the (100) orientation in the base layer containing MgO as a main component, for example, a Ta base layer may be formed on a glass substrate and MgO as a main component may be formed on the Ta base layer. . When a Cr layer or an alloy layer having a BCC structure mainly composed of Cr is formed on a heated glass substrate, the Cr layer or the Cr alloy layer exhibits (100) orientation. Therefore, by forming an MgO layer on this, the (100) orientation can be taken in the MgO layer. Specific examples of the Cr alloy include CrTi, CrMo, CrV, CrW, CrMo, CrRu, and CrMn.
　本発明の熱アシスト磁気記録媒体において、基板上に形成された複数の下地層は、その少なくとも一つが、上記のＭｇＯを主成分とし、かつ、特定の酸化物を含む下地層であることが必須であるが、その他の下地層は格別限定されるものではなく、一般の磁気記録媒体と同様なものを用いることができる。ＭｇＯを主成分とする下地層以外の下地層の例としては、上記のＴａからなる配向制御層；および、上記のＣｒからなる、またはＣｒを主成分とするＢＣＣ構造を有する合金からなる配向制御層；Ｃｕ、Ａｇ、Ａｌもしくはこれらを主成分とする熱伝導率の高い合金材料からなるヒートシンク層；書き込み特性を改善するため、Ｃｏからなる、またはＣｏを主成分とする軟磁性下地層などが挙げられる。更に、基板との密着性を改善するための密着層を形成することもできる。 In the thermally-assisted magnetic recording medium of the present invention, it is essential that at least one of the plurality of underlayers formed on the substrate is an underlayer containing the above MgO as a main component and containing a specific oxide. However, the other underlayers are not particularly limited, and those similar to general magnetic recording media can be used. Examples of the foundation layer other than the foundation layer mainly composed of MgO include the orientation control layer composed of the above-mentioned Ta; and the orientation control composed of the above-described Cr or an alloy having a BCC structure mainly composed of Cr. Layer: Cu, Ag, Al or a heat sink layer made of an alloy material having a high thermal conductivity containing these as a main component; a soft magnetic underlayer made of Co or the main component of Co for improving write characteristics Can be mentioned. Furthermore, an adhesion layer for improving adhesion with the substrate can be formed.
　以下、実施例により本発明を具体的に説明する。本発明は、以下の実施例に限定されるものではなく、その要旨を変更しない範囲で適宜変更して実施することができる。 Hereinafter, the present invention will be specifically described by way of examples. The present invention is not limited to the following examples, and can be implemented with appropriate modifications without departing from the scope of the invention.
（実施例１－１～１－１４、比較例１）
　図１に本実施例で作製した磁気記録媒体の層構成の一例を示す。本実施例では耐熱ガラス基板(１０１)上に３０ｎｍ厚のＮｉ－５０原子（aｔ）％Ｔｉ合金下地層(１０２)、２５ｎｍ厚のＣｏ－２０ａｔ％Ｔａ－５ａｔ％Ｂ合金からなる軟磁性下地層(１０３)を形成し、２５０℃まで加熱したのち、１０ｎｍ厚のＣｒ層(１０４)を形成した。その後、ＭｇＯを主成分とする下地層(１０５)を５ｎｍ形成し、基板を４２０℃まで加熱した後、６ｎｍ厚の（Ｆｅ－５５ａｔ％Ｐｔ）－１８ｍｏｌ％ＴｉＯ２磁性層(１０６)、３ｎｍ厚のカーボン保護膜(１０７)を形成した。 (Examples 1-1 to 1-14, Comparative Example 1)
FIG. 1 shows an example of the layer structure of the magnetic recording medium produced in this example. In this embodiment, a Ni-50 atom (at)% Ti alloy underlayer (102) having a thickness of 30 nm and a Co-20 at% Ta-5 at% B alloy having a thickness of 25 nm are formed on a heat-resistant glass substrate (101). After forming (103) and heating to 250 ° C., a 10 nm thick Cr layer (104) was formed. Thereafter, an underlayer (105) containing MgO as a main component is formed to 5 nm, the substrate is heated to 420 ° C., and then a 6 nm thick (Fe-55 at% Pt) -18 mol% TiO 2 magnetic layer (106), 3 nm thick A carbon protective film (107) was formed.
　ＭｇＯを主成分とする下地層には、ＭｇＯ－１０ｍｏｌ％ＳｉＯ２、ＭｇＯ－２ｍｏｌ％ＴｉＯ２、ＭｇＯ－５ｍｏｌ％ＳｉＯ２－５ｍｏｌＴｉＯ２、ＭｇＯ－８ｍｏｌ％Ｃｒ２Ｏ３、ＭｇＯ－５ｍｏｌ％Ａｌ２Ｏ３、ＭｇＯ－２ｍｏｌ％Ｔａ２Ｏ５、ＭｇＯ－５ｍｏｌ％ＳｉＯ２－５ｍｏｌ％Ｔａ２Ｏ５、ＭｇＯ－１５ｍｏｌ％ＺｒＯ２、ＭｇＯ－１０ｍｏｌ％Ｙ２Ｏ３、ＭｇＯ－１０ｍｏｌ％Ｙ２Ｏ３－１０ｍｏｌＴｉＯ、ＭｇＯ－５ｍｏｌ％ＣｅＯ２、ＭｇＯ－１２ｍｏｌ％ＭｎＯ、ＭｇＯ－２０ｍｏｌ％ＴｉＯ、ＭｇＯ－１５ｍｏｌ％ＺｎＯを使用した。また、比較例として、酸化物を添加しないＭｇＯ下地層を使用した媒体を作製した。 For the underlayer containing MgO as a main component, MgO-10 mol% SiO 2 , MgO-2 mol% TiO 2 , MgO-5 mol% SiO 2 -5 mol TiO 2 , MgO-8 mol% Cr 2 O 3 , MgO-5 mol% Al 2 O 3 , MgO-2 mol% Ta 2 O 5 , MgO-5 mol% SiO 2 -5 mol% Ta 2 O 5 , MgO-15 mol% ZrO 2 , MgO-10 mol% Y 2 O 3 , MgO-10 mol% Y 2 O 3 −10 mol TiO, MgO—5 mol% CeO 2 , MgO—12 mol% MnO, MgO—20 mol% TiO, MgO—15 mol% ZnO were used. Further, as a comparative example, a medium using an MgO underlayer to which no oxide was added was produced.
　本実施例媒体のＸ線回折測定を行ったところ、何れの媒体においても、Ｃｒ下地層からの強いＢＣＣ（２００）ピークが観測された。また、磁性層からは強いＬ１ｏ－ＦｅＰｔ（００１）回折ピーク、及びＬ１ｏ－ＦｅＰｔ（００２）ピークとＦＣＣ－Ｆｅ（２００）ピークの混合ピークが観測された。後者の混合ピークに対する前者のピークの積分強度比は１．６～１．８で、規則度の高いＬ１ｏ型ＦｅＰｔ合金結晶が形成されていることがわかった。 When X-ray diffraction measurement was performed on the medium of this example, a strong BCC (200) peak from the Cr underlayer was observed in any medium. Further, strong L1 o -FePt (001) diffraction peaks and mixed peaks of L1 o -FePt (002) peaks and FCC-Fe (200) peaks were observed from the magnetic layer. The integrated intensity ratio of the former peak to the latter mixed peak was 1.6 to 1.8, and it was found that L1 o- type FePt alloy crystals with high degree of order were formed.
　表１に本実施例媒体、及び比較例媒体の保磁力Ｈｃ、及び保磁力分散ΔＨｃ／Ｈｃの値を示す。ここで、ΔＨｃ／Ｈｃは、ＩＥＥＥ　Ｔｒａｎｓ．　Ｍａｇｎ．，　ｖｏｌ．　２７，　ｐｐ４９７５－４９７７，　１９９１に記載の方法を用いて室温で測定した。具体的には、メジャーループ及びマイナーループにおいて、磁化の値が飽和値の５０％となるときの磁界を測定し、両者の差分から、Ｈｃ分布がガウス分布であると仮定してΔＨｃ／Ｈｃを算出した。 Table 1 shows values of the coercive force Hc and the coercive force dispersion ΔHc / Hc of the medium of this example and the comparative example. Here, ΔHc / Hc is the value of IEEE Trans. Magn. , Vol. 27, pp 4975-4977, 1991, and measured at room temperature. Specifically, in the major loop and the minor loop, the magnetic field when the magnetization value is 50% of the saturation value is measured, and ΔHc / Hc is calculated from the difference between the two assuming that the Hc distribution is a Gaussian distribution. Calculated.
　本実施例媒体のΔＨｃ／Ｈｃは、いずれも０．３以下の低い値であったのに対し、比較例媒体のΔＨｃ／Ｈｃは、０．５２と実施例媒体よりも著しく高い値を示した。これより、ＭｇＯ下地層に、ＳｉＯ２等の酸化物を添加することによって、保持力分散を低減できることがわかった。 The ΔHc / Hc of the example medium was a low value of 0.3 or less, whereas the ΔHc / Hc of the comparative example medium was 0.52, which was significantly higher than that of the example medium. . Thus, it was found that dispersion of coercive force can be reduced by adding an oxide such as SiO 2 to the MgO underlayer.
　なお、磁性層には、上記ＦｅＰｔ－ＴｉＯ２の他に、ＦｅＰｔ－ＳｉＯ２、ＦｅＰｔ－Ｃｒ２Ｏ３、ＦｅＰｔ－Ａｌ２Ｏ３、ＦｅＰｔ－Ｔａ２Ｏ５、ＦｅＰｔ－ＺｒＯ２、ＦｅＰｔ－Ｙ２Ｏ３、ＦｅＰｔ－ＣｅＯ２、ＦｅＰｔ－ＭｎＯ、ＦｅＰｔ－ＴｉＯ、ＦｅＰｔ－ＺｎＯを用いた場合も同様に、ＭｇＯと酸化物戸からなる下地層を形成することによって、保持力分散を低減できることがわかった。また、Ｌ１０構造を有するＣｏＰｔ合金と上記酸化物、もしくはＣからなる磁性層を用いても良い。 In addition to the above FePt—TiO 2 , the magnetic layer includes FePt—SiO 2 , FePt—Cr 2 O 3 , FePt—Al 2 O 3 , FePt—Ta 2 O 5 , FePt—ZrO 2 , FePt—Y. Similarly, when 2 O 3 , FePt—CeO 2 , FePt—MnO, FePt—TiO, and FePt—ZnO are used, the dispersion of coercive force can be reduced by forming an underlayer composed of MgO and an oxide door. all right. It is also possible to use a magnetic layer made of CoPt alloy and the oxide, or C having an L1 0 structure.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
（実施例２－１～２－８）
　図２に本実施例で作製した磁気記録媒体の層構成の他の一例を示す。本実施例では、耐熱ガラス基板（２０１）上に１０ｎｍ厚のＮｉ－５０ａｔ％Ｔａ合金シード層（２０２）、５０ｎｍ厚のＣｏ－２８ａｔ％Ｆｅ－５ａｔ％Ｚｒ－３ａｔ％Ｔａ合金からなる軟磁性下地層（２０３）、７ｎｍ厚のＴａ下地層（２０４）を形成した。その後、ＭｇＯを主成分とする下地層（２０５）を３ｎｍ形成し、基板を４５０℃まで加熱した後、１０ｎｍ厚の（Ｆｅ－５０ａｔ％Ｐｔ－１０ａｔ％Ｃｕ）－４０ａｔ％Ｃ磁性層（２０６）、３ｎｍ厚のカーボン保護膜（２０７）を形成した。 (Examples 2-1 to 2-8)
FIG. 2 shows another example of the layer structure of the magnetic recording medium manufactured in this example. In this example, a soft magnetic substrate comprising a Ni-50 at% Ta alloy seed layer (202) with a thickness of 10 nm and a Co-28 at% Fe-5 at% Zr-3 at% Ta alloy with a thickness of 50 nm on a heat resistant glass substrate (201). A base layer (203) and a 7 nm thick Ta underlayer (204) were formed. Thereafter, an underlayer (205) containing MgO as a main component is formed to 3 nm, the substrate is heated to 450 ° C., and then a 10 nm thick (Fe-50 at% Pt-10 at% Cu) -40 at% C magnetic layer (206) A carbon protective film (207) having a thickness of 3 nm was formed.
　ＭｇＯを主成分とする下地層には、ＭｇＯ－１８ｍｏｌ％ＳｉＯ２、ＭｇＯ－５ｍｏｌ％ＳｉＯ２－５ｍｏｌ％Ｃｒ２Ｏ３、ＭｇＯ－５ｍｏｌ％ＴｉＯ２－Ｃｒ２Ｏ３、ＭｇＯ－４ｍｏｌ％ＴｉＯ２－３ａｔ％ＺｒＯ２、ＭｇＯ－８ｍｏｌ％Ｃｒ２Ｏ３、ＭｇＯ－１０ｍｏｌ％Ａｌ２Ｏ３－３ａｔ％Ｔａ２Ｏ５、ＭｇＯ－５ｍｏｌ％Ｙ２Ｏ３、ＭｇＯ－１０ａｔ％ＴｉＯ－２ｍｏｌＺｎＯを使用した。
　また、比較例として、酸化物を添加しないＭｇＯ下地層を使用した媒体を作製した。更に、ＭｇＯを主成分とする下地層の平面ＴＥＭ観察を行うため、該ＭｇＯを主成分とする下地層の上に磁性層を形成しない試料を作製した。 The underlayer mainly composed of MgO includes MgO-18 mol% SiO 2 , MgO-5 mol% SiO 2 -5 mol% Cr 2 O 3 , MgO-5 mol% TiO 2 —Cr 2 O 3 , MgO-4 mol% TiO 2. -3at% ZrO 2, MgO-8mol % Cr 2 O 3, MgO-10mol% Al 2 O 3 -3at% Ta 2 O 5, MgO-5mol% Y 2 O 3, were used MgO-10at% TiO-2molZnO .
Further, as a comparative example, a medium using an MgO underlayer to which no oxide was added was produced. Furthermore, in order to perform planar TEM observation of the base layer containing MgO as a main component, a sample was prepared in which no magnetic layer was formed on the base layer containing MgO as a main component.
　上記磁性層を形成しない試料を用いて、ＭｇＯを主成分とする下地層の平面ＴＥＭ観察を行い、平均粒径を測定したところ、ＭｇＯを主成分とする下地層の平均粒径は概ね５－１０ｎｍであった。一方、酸化物を添加しないＭｇＯ下地層の平均粒径は３０ｎｍ以上であった。 Using the sample that does not form the magnetic layer, a planar TEM observation of the underlayer containing MgO as a main component was performed and the average particle size was measured. It was 10 nm. On the other hand, the average particle size of the MgO underlayer to which no oxide was added was 30 nm or more.
　次に、磁性層を形成した本実施例媒体の平面ＴＥＭ観察を行った。表２に、本実施例媒体の磁性層の平均粒径＜Ｄ＞、及び平均粒径で規格化した粒径分散σ／＜Ｄ＞の値を示す。本実施例媒体の平均粒径はいずれも５．５－６．４ｎｍの範囲内であった。また、平均粒径で規格化した粒径分散σ／＜Ｄ＞は、０．２２以下の低い値を示した。これに対して比較例媒体の磁性層の平均粒径は本実施例媒体とほぼ同程度であったが、平均粒径で規格化した粒径分散σ／＜Ｄ＞は０．３２であり、実施例媒体に比べて著しく高かった。 Next, planar TEM observation of the medium of the present example on which the magnetic layer was formed was performed. Table 2 shows the average particle size <D> of the magnetic layer of the medium of this example and the value of particle size dispersion σ / <D> normalized by the average particle size. The average particle diameter of the media of this example was in the range of 5.5 to 6.4 nm. The particle size dispersion σ / <D> normalized by the average particle size showed a low value of 0.22 or less. In contrast, the average particle size of the magnetic layer of the comparative example medium was almost the same as that of the medium of this example, but the particle size dispersion σ / <D> normalized by the average particle size is 0.32. It was significantly higher than the example medium.
　これは、上述の様に、酸化物を添加しないＭｇＯ下地層の結晶粒径が、実施例媒体に比べて大きくなっているためと考えられる。以上より、ＭｇＯに酸化物を添加した下地層を用いることにより、粒径分散が低減され、磁性層中の結晶粒の粒子サイズを均一化できることが明らかになった。 This is presumably because the crystal grain size of the MgO underlayer to which no oxide is added is larger than that of the example medium as described above. From the above, it has been clarified that the use of an underlayer obtained by adding an oxide to MgO can reduce the particle size dispersion and make the crystal grain size in the magnetic layer uniform.
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
（電磁変換特性評価）
　上記実施例２－１～２－８で示した媒体にパーフルオルポリエーテル系の潤滑剤を塗布したのち、図３に示した磁気記憶装置に組み込んだ。本磁気記憶装置は、磁気記録媒体（７０１）と、磁気記録媒体（７０１）を回転させるための駆動部（７０２）と、磁気ヘッド（７０３）と、ヘッドを移動させるための駆動部（７０）と、記録再生信号処理系（７０５）から構成される。 (Electromagnetic conversion characteristics evaluation)
A perfluoropolyether lubricant was applied to the media shown in Examples 2-1 to 2-8, and then incorporated into the magnetic memory device shown in FIG. The magnetic storage device includes a magnetic recording medium (701), a driving unit (702) for rotating the magnetic recording medium (701), a magnetic head (703), and a driving unit (70) for moving the head. And a recording / reproducing signal processing system (705).
　図４に磁気ヘッドの構成を示す。記録用ヘッド（８０１）は、上部磁極（８０２）、下部磁極（８０３）、及び両者の間に挟まれたＰＳＩＭ（Ｐｌａｎａｒ　Ｓｏｌｉｄ　Ｉｍｍｅｒｓｉｏｎ　Ｍｉｒｒｏｒ）（８０４）から構成される。ＰＳＩＭは、例えば、Ｊｐｎ．，　Ｊ．　Ａｐｐｌ．　Ｐｈｙｓ．，　Ｖｏｌ４５，　Ｎｏ．２Ｂ，　ｐｐ１３１４－１３２０　（２００６）に記載されている構造のものを用いることができる。すなわち、ＰＳＩＭ（８０４）の先端部には、近接場光発生部（８０５）が形成されている。そして、ＰＳＩＭのＧｒａｔｉｎｇ部（８０６）にレーザー光源（８０７）から、例えば波長６５０ｎｍの半導体レーザー（８０８）を照射し、ＰＳＩＭ先端部の近接場光発生部にレーザー光を集光させ、近接場光発生部から発生した近接場光（８０９）により媒体（８１０）を加熱できる。尚、レーザー波長は、近接場光発生部の材質、形状によって決まる最適な励起波長に近い波長を選択するが望ましい。再生ヘッド（８１１）は、上部シールド（８１２）および下部シールド（８１３）と、これらに挟まれたＴＭＲ素子（８１４）で構成されている。 Fig. 4 shows the configuration of the magnetic head. The recording head (801) includes an upper magnetic pole (802), a lower magnetic pole (803), and a PSIM (Planar Solid Immersion Mirror) (804) sandwiched therebetween. PSIM is, for example, Jpn. , J. Appl. Phys. , Vol45, No. 2B, pp1314-1320 (2006) can be used. That is, a near-field light generating part (805) is formed at the tip of the PSIM (804). Then, the semiconductor light source (808) having a wavelength of 650 nm, for example, is irradiated from the laser light source (807) to the PSIM grating unit (806), and the near-field light is condensed on the near-field light generation unit at the PSIM tip. The medium (810) can be heated by the near-field light (809) generated from the generation unit. As the laser wavelength, it is desirable to select a wavelength close to the optimum excitation wavelength determined by the material and shape of the near-field light generating part. The reproducing head (811) includes an upper shield (812) and a lower shield (813), and a TMR element (814) sandwiched between them.
　上記ヘッドで、本実施例媒体を加熱し、線記録密度１６００ｋＦＣＩ（ｋｉｌｏ　Ｆｌｕｘ　ｃｈａｎｇｅｓ　ｐｅｒ　Ｉｎｃｈ）の信号を記録し、電磁変換特性を測定した。表３に測定結果を示す。ここで、重ね書き特性（ＯＷ）は、８００ｋＦＣＩの信号を書き込んだ後、１０７ｋＦＣＩの信号を重ね書きし、８００ｋＦＣＩの信号の残り成分を評価した。本実施例媒体は、いずれも、１５．３ｄＢ以上の高い媒体ＳＮ比（ＳＮＲ）と、３０．１ｄＢ以上の良好な重ね書き特性を示した。一方、酸化物を添加しないＭｇＯ下地層を用いた比較例媒体のＳＮＲと重ね書き特性は、実施例媒体に比べて大幅に低かった。これは、磁性結晶の粒径分散が大きかったためと考えられる。以上より、ＭｇＯに酸化物を添加した下地層を用いることにより、高い媒体ＳＮＲと良好な重ね書き特性を有する熱アシスト媒体が得られることがわかった。 The medium of this example was heated with the above-mentioned head, a signal with a linear recording density of 1600 kFCI (kilo flux changes per inch) was recorded, and the electromagnetic conversion characteristics were measured. Table 3 shows the measurement results. Here, for the overwrite characteristic (OW), after writing an 800 kFCI signal, a 107 kFCI signal was overwritten, and the remaining components of the 800 kFCI signal were evaluated. All of the media of this example exhibited a high medium SN ratio (SNR) of 15.3 dB or more and good overwrite characteristics of 30.1 dB or more. On the other hand, the SNR and the overwriting characteristics of the comparative example medium using the MgO underlayer to which no oxide was added were significantly lower than those of the example medium. This is presumably because the particle size dispersion of the magnetic crystals was large. From the above, it was found that a heat-assisted medium having a high medium SNR and good overwriting characteristics can be obtained by using an underlayer obtained by adding an oxide to MgO.
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000003
１０１…ガラス基板
１０２…ＮｉＴｉ下地層
１０３…軟磁性下地層
１０４…Ｃｒ下地層
１０５…ＭｇＯを主成分とする層
１０６…磁性層
１０７…カーボン保護膜
２０１…ガラス基板
２０２…ＮｉＴａ下地層
２０３…軟磁性下地層
２０４…Ｔａ下地層
２０５…ＭｇＯを主成分とする層
２０６…磁性層
２０７…カーボン保護膜
７０１…磁気記録媒体
７０２…媒体駆動部
７０３…磁気ヘッド
７０…ヘッド駆動部
７０５…記録再生信号処理系
８０１…記録ヘッド
８０２…上部磁極
８０３…下部磁極
８０４…ＰＳＩＭ（Ｐｌａｎａｒ　Ｓｏｌｉｄ　Ｉｍｍｅｒｓｉｏｎ　Ｍｉｒｒｏｒ）
８０５…近接場光発生部
８０６…Ｇｒａｔｉｎｇ部
８０７…レーザー光源
８０８…半導体レーザー
８０９…近接場光
８１０…媒体
８１１…再生ヘッド
８１２…上部シールド
８１３…下部シールド
８１４…ＴＭＲ素子 DESCRIPTION OF SYMBOLS 101 ... Glass substrate 102 ... NiTi underlayer 103 ... Soft magnetic underlayer 104 ... Cr underlayer 105 ... MgO main layer 106 ... Magnetic layer 107 ... Carbon protective film 201 ... Glass substrate 202 ... NiTa underlayer 203 ... Soft Magnetic underlayer 204... Ta underlayer 205... MgO main layer 206. Magnetic layer 207. Carbon protective film 701. Magnetic recording medium 702... Medium driving unit 703. Processing system 801 ... Recording head 802 ... Upper magnetic pole 803 ... Lower magnetic pole 804 ... PSIM (Planar Solid Immersion Mirror)
805... Near-field light generating unit 806... Grafting unit 807. Laser light source 808... Semiconductor laser 809 .. Near-field light 810 ... Medium 811 ... Reproducing head 812 ... Upper shield 813 ... Lower shield 814 ... TMR element
　本発明の熱アシスト記録媒体は、磁性結晶粒が微細で粒径分散が低く、磁性粒子間の交換結合が十分に弱く、かつ、保磁力分散が低いという特長を有する。したがって、この熱アシスト記録媒体を用いた磁気記憶装置は、電磁変換特性、特に、ＳＮ比と書き込み性に優れており、高密度記録が可能な磁気記録方式として広く利用されることが期待される。 The heat-assisted recording medium of the present invention has the characteristics that the magnetic crystal grains are fine, the particle size dispersion is low, the exchange coupling between the magnetic particles is sufficiently weak, and the coercive force dispersion is low. Therefore, a magnetic storage device using this heat-assisted recording medium is expected to be widely used as a magnetic recording method capable of high-density recording because of excellent electromagnetic conversion characteristics, in particular, SN ratio and writability. .

Claims (9)

  1. 　基板と、該基板上に形成された複数の下地層と、Ｌ１０構造を有する合金を主成分とする磁性層を有する磁気記録媒体において、該下地層の少なくとも一つが、ＭｇＯを主成分とし、かつ、ＳｉＯ２、ＴｉＯ２、Ｃｒ２Ｏ３、Ａｌ２Ｏ３、Ｔａ２Ｏ５、ＺｒＯ２、Ｙ２Ｏ３、ＣｅＯ２、ＭｎＯ、ＴｉＯおよびＺｎＯから選択される少なくとも一種類の酸化物を含有していることを特徴とする熱アシスト磁気記録媒体。 A substrate, a plurality of base layer formed on the substrate, a magnetic recording medium having a magnetic layer mainly composed of an alloy having an L1 0 structure, at least one underlayer is composed mainly of MgO, And at least one oxide selected from SiO 2 , TiO 2 , Cr 2 O 3 , Al 2 O 3 , Ta 2 O 5 , ZrO 2 , Y 2 O 3 , CeO 2 , MnO, TiO and ZnO. A heat-assisted magnetic recording medium comprising:
  2. 　ＭｇＯを主成分とする下地層に含まれる酸化物の量が、下地層全体に基づき、２ｍｏｌ％～４０ｍｏｌ％の範囲内である請求項１に記載の熱アシスト磁気記録媒体。 The heat-assisted magnetic recording medium according to claim 1, wherein the amount of oxide contained in the underlayer containing MgO as a main component is in the range of 2 mol% to 40 mol% based on the entire underlayer.
  3. 　ＭｇＯを主成分とする下地層が、Ｃｒからなる層、またはＣｒを主成分とするＢＣＣ構造を有するＣｒ合金からなる下地層上に形成されている請求項１または２に記載の熱アシスト磁気記録媒体。 3. The thermally assisted magnetic recording according to claim 1, wherein the base layer mainly composed of MgO is formed on a layer composed of Cr or a base layer composed of Cr alloy having a BCC structure mainly composed of Cr. Medium.
  4. 　ＭｇＯを主成分とする下地層が、Ｔａ下地層上に形成されている請求項１または２に記載の熱アシスト磁気記録媒体。 The heat-assisted magnetic recording medium according to claim 1, wherein the underlayer mainly composed of MgO is formed on the Ta underlayer.
  5. 　ＭｇＯを主成分とする下地層の平均粒径が１０ｎｍ以下である請求項１乃至４の何れか１項に記載の熱アシスト磁気記録媒体。 The heat-assisted magnetic recording medium according to any one of claims 1 to 4, wherein an average particle diameter of the underlayer mainly composed of MgO is 10 nm or less.
  6. 　磁性層がＬ１０構造を有するＦｅＰｔまたはＣｏＰｔ合金を主成分とし、かつ、ＳｉＯ２、ＴｉＯ２、Ｃｒ２Ｏ３、Ａｌ２Ｏ３、Ｔａ２Ｏ５、ＺｒＯ２、Ｙ２Ｏ３、ＣｅＯ２、ＭｎＯ、ＴｉＯ、ＺｎＯ、Ｃから選択される少なくとも一種類の酸化物または元素を含有している請求項１乃至５の何れか１項に記載の熱アシスト磁気記録媒体。 The magnetic layer is mainly composed of FePt or CoPt alloy having an L1 0 structure, and SiO 2 , TiO 2 , Cr 2 O 3 , Al 2 O 3 , Ta 2 O 5 , ZrO 2 , Y 2 O 3 , CeO 2. The heat-assisted magnetic recording medium according to claim 1, comprising at least one kind of oxide or element selected from MnO, TiO, ZnO, and C.
  7. 　磁性層に含まれる酸化物の量が、磁性層全体に基づき、１０ｍｏｌ％以上、４０ｍｏｌ％以下の範囲内である請求項６に記載の熱アシスト磁気記録媒体。 The heat-assisted magnetic recording medium according to claim 6, wherein the amount of oxide contained in the magnetic layer is in the range of 10 mol% or more and 40 mol% or less based on the entire magnetic layer.
  8. 磁性層に含まれるＣの量が、磁性層全体に基づき、１０ａｔ％以上、７０ａｔ％以下の範囲内である請求項６に記載の熱アシスト磁気記録媒体。 The thermally assisted magnetic recording medium according to claim 6, wherein the amount of C contained in the magnetic layer is in the range of 10 at% or more and 70 at% or less based on the entire magnetic layer.
  9. 　磁気記録媒体と、該磁気記録媒体を回転させるための駆動部と、該磁気記録媒体を加熱するためのレーザー発生部と、該レーザー発生部から発生したレーザー光をヘッド先端まで導く導波路と、ヘッド先端に取り付けられた近接場光発生部を備えた磁気ヘッドと、該磁気ヘッドを移動させるための駆動部と、記録再生信号処理系から構成さる磁気記憶装置において、該磁気記録媒体が請求項１乃至８の何れかに記載の熱アシスト媒体であることを特徴とする磁気記憶装置。 A magnetic recording medium, a driving unit for rotating the magnetic recording medium, a laser generating unit for heating the magnetic recording medium, and a waveguide for guiding laser light generated from the laser generating unit to the tip of the head, In a magnetic storage device comprising a magnetic head having a near-field light generating unit attached to the tip of the head, a driving unit for moving the magnetic head, and a recording / reproducing signal processing system, the magnetic recording medium is claimed. A magnetic storage device, which is the heat-assisted medium according to any one of 1 to 8.
PCT/JP2011/052238 2010-02-04 2011-02-03 Thermally assisted magnetic recording medium and magnetic storage device WO2011096472A1 (en)

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